Any discussion of the related art throughout this specification should in no way be considered as an admission that such art is widely known or forms part of the common general knowledge in the field.
Nanotube fabric layers and films are used in a plurality of electronic structures, and devices. For example, U.S. patent application Ser. No. 11/835,856 to Bertin et al., incorporated herein by reference in its entirety, teaches methods of using nanotube fabric layers to realize nonvolatile devices such as, but not limited to, block switches, programmable resistive elements, and programmable logic devices. U.S. Pat. No. 7,365,632 to Bertin et al., incorporated herein by reference in its entirety, teaches the use of such fabric layers and films within the fabrication of thin film nanotube based resistors. U.S. patent application Ser. No. 12/066,063, now U.S. Pat. No. 7,927,992, to Ward et al., incorporated herein by reference in its entirety, teaches the use of such nanotube fabrics and films to form heat transfer elements within electronic devices and systems. U.S. patent application entitled “Microstrip Antenna Elements and Arrays Comprising a Shaped Carbon Nanotube Layer and Integrated Two Terminal Nanotube Select Devices,” filed on even date with the present disclosure (U.S. patent application Ser. No. not yet assigned) teaches the use of such nanotube fabrics and films in the fabrication of microstrip antenna elements and arrays.
Through a variety of previously know techniques (described in more detail within the incorporated references) nanotube elements can be rendered conducting, non-conducting, or semi-conducting before or after the formation of a nanotube fabric layer or film, allowing such nanotube fabric layers and films to serve a plurality of functions within an electronic device or system. Further, in some cases the electrical conductivity of a nanotube fabric layer or film can be adjusted between two or more non-volatile states as taught in U.S. patent application Ser. No. 11/280,786, now U.S. Pat. No. 7,781,862, to Bertin et al., incorporated herein by reference in its entirety, allowing for such nanotube fabric layers and films to be used as memory or logic elements within an electronic system.
U.S. Pat. No. 7,334,395 to Ward et al., incorporated herein by reference in its entirety, teaches a plurality of methods for forming nanotube fabric layers and films on a substrate element using preformed nanotubes. The methods include, but are not limited to, spin coating (wherein a solution of nanotubes is deposited on a substrate which is then spun to evenly distribute said solution across the surface of said substrate), spray coating (wherein a plurality of nanotube are suspended within an aerosol solution which is then disbursed over a substrate), and in situ growth of nanotube fabric (wherein a thin catalyst layer is first deposited over a substrate and then used to faun nanotubes). Further, U.S. Pat. No. 7,375,369 to Sen et al., incorporated herein by reference in its entirety, teaches a nanotube solution which is well suited for forming a nanotube fabric layer over a substrate element via a spin coating process.
Within the current state of the art, there is an increasing need for nanotube fabric layers and films which are relatively thin, highly transparent, and possess a low uniform sheet resistance. Further, there is also a need for such nanotube fabrics layers and films to possess minimal voids (gaps or spaces between the individual nanotube elements) such as to provide substantially uniform electrical and mechanical properties throughout the nanotube fabric layer and film. To this end, it would be advantageous if methods were developed such that nanotube fabric layers and films could be readily formed in an anisotropic state. That is, if such nanotube fabric layers and films could be formed such that the individual nanotube elements within said layers and films were all oriented in substantially the same direction. In this way, very dense nanotube fabric layers and films could be realized with said layers and films possessing substantially uniform electrical characteristics and relatively low sheet resistance. Further, such nanotube fabric layers and films could be formed using minimal layers, maximizing the optical transparency through said fabric layers and films.